An accumulator piston of this type is known for example from DE 101 35 544 A1. This known accumulator piston has a piston shaft which is designed as a hollow cylinder and via which the accumulator piston is displaceably received and axially guided in a cylinder. A piston head is formed at one end of this piston shaft. This piston head covers the open cross-section of the hollow cylindrical piston shaft and thereby forms an end face of the accumulator piston which faces the environment of the accumulator piston and can be acted upon by pressure medium.
Pressure medium accumulators which are constructed in this way are used in electronically slip-controllable vehicle brake systems in order to buffer pressure medium which has been discharged from wheel brakes in the course of a brake pressure control. They are connected upstream of pressure generators, which subsequently supply the buffered pressure medium to a brake circuit for further pressure build up or convey pressure medium volumes which are not required back to a supply container again after completion of a braking procedure.
Pressure medium can disadvantageously contain impurities. If these are particles with a high hardness, for example metal chips, these particles can damage sealing and/or guide rings arranged at the circumference of the accumulator piston. Furthermore, particles which penetrate into gaps between mutually relatively movable components block this relative movement and, in an extreme case, thereby trigger a system failure. The latter can also occur at components controlling the brake pressure, which are arranged downstream of the pressure medium accumulator or are supplied with pressure medium from the pressure medium accumulator.